#! /usr/bin/env python
"""Creates an OData in-memory cache of key value pairs"""

# SAMPLE_DIR='small-sample'
SAMPLE_DIR = 'daily-text'
SAMPLE_DB = 'weather.db'

SERVICE_PORT = 8080
SERVICE_ROOT = "http://localhost:%i/" % SERVICE_PORT

import logging
import threading
import time
import string
import os
import StringIO
import os.path
from wsgiref.simple_server import make_server

import pyslet.iso8601 as iso
import pyslet.odata2.csdl as edm
import pyslet.odata2.core as core
import pyslet.odata2.metadata as edmx
from pyslet.odata2.server import ReadOnlyServer
from pyslet.odata2.sqlds import SQLiteEntityContainer
from pyslet.odata2.memds import InMemoryEntityContainer
import pyslet.rfc2616 as http


def LoadMetadata(path='WeatherSchema.xml'):
    """Loads the metadata file from the current directory."""
    doc = edmx.Document()
    with open(path, 'rb') as f:
        doc.Read(f)
    return doc


def MakeContainer(doc, drop=False, path=SAMPLE_DB):
    if drop and os.path.isfile(path):
        os.remove(path)
    create = not os.path.isfile(path)
    container = SQLiteEntityContainer(
        filePath=path,
        containerDef=doc.root.DataServices['WeatherSchema.CambridgeWeather'])
    if create:
        container.CreateAllTables()


def IsBST(t):
    """Returns True/False/Unknown if the timepoint t is in BST

    This function uses the last Sunday in the month algorithm even
    though most sources say that prior to 1996 the rule was different.
    The only date of contention in this data set is 1995-10-22 which
    should have a clock change but the data set clearly have a change on
    1995-10-29, a week later."""
    century, year, month, day = t.date.GetCalendarDay()
    if month < 3:
        return False
    elif month == 3:
        if day < 24:
            return False
        # deal with switch to BST
        century, decade, year, week, weekday = t.date.GetWeekDay()
        if weekday == 7:
            # Sunday - look deeper
            hour, minute, second = t.time.GetTime()
            if hour <= 1:
                return False
            else:
                return True
        elif day + (7 - weekday) > 31:
            # next Sunday's date is in April, we already changed
            return True
        else:
            # next Sunday's date is in March, we haven't changed yet
            return False
    elif month < 10:
        return True
    elif month == 10:
        if day < 24:
            return True
        # deal with switch to GMT
        century, decade, year, week, weekday = t.date.GetWeekDay()
        if weekday == 7:
            # Sunday - look deeper
            hour, minute, second = t.time.GetTime()
            if hour < 1:
                return True
            elif hour > 1:
                return False
            else:
                return None		# Ambiguous time
        elif day + (7 - weekday) > 31:
            # next Sunday's date is in November, we already changed
            return False
        else:
            # next Sunday's date is in October, we haven't changed yet
            return True
    else:
        return False


def LoadDataFromFile(weatherData, f, year, month, day):
    with weatherData.OpenCollection() as collection:
        while True:
            line = f.readline()
            if len(line) == 0:
                break
            elif line[0] == '#':
                continue
            data = line.split()
            if not data:
                continue
            if len(data) < 11:
                data = data + ['*'] * (11 - len(data))
            for i in (1, 3, 5, 7, 8, 10):
                try:
                    data[i] = float(data[i])
                except ValueError:
                    data[i] = None
            for i in (2, 4, 6):
                try:
                    data[i] = int(data[i])
                except ValueError:
                    data[i] = None
            dataPoint = collection.NewEntity()
            hour, min = map(int, data[0].split(':'))
            tValue = iso.TimePoint(
                date=iso.Date(century=year / 100, year=year %
                              100, month=month, day=day),
                time=iso.Time(hour=hour, minute=min, second=0))
            bst = IsBST(tValue)
            if bst is not False:
                # assume BST for now, add the zone info and then shift to GMT
                tValue = tValue.WithZone(
                    zDirection=1, zHour=1).ShiftZone(zDirection=0)
            dataPoint['TimePoint'].SetFromValue(tValue)
            dataPoint['Temperature'].SetFromValue(data[1])
            dataPoint['Humidity'].SetFromValue(data[2])
            dataPoint['DewPoint'].SetFromValue(data[3])
            dataPoint['Pressure'].SetFromValue(data[4])
            dataPoint['WindSpeed'].SetFromValue(data[5])
            dataPoint['WindDirection'].SetFromValue(data[6])
            dataPoint['Sun'].SetFromValue(data[7])
            dataPoint['Rain'].SetFromValue(data[8])
            shour, smin = map(int, data[9].split(':'))
            dataPoint['SunRainStart'].SetFromValue(
                iso.Time(hour=shour, minute=smin, second=0))
            dataPoint['WindSpeedMax'].SetFromValue(data[10])
            try:
                collection.InsertEntity(dataPoint)
            except edm.ConstraintError:
                if bst is None:
                    # This was an ambiguous entry, the first one is in BST, the
                    # second one is in GMT as the clocks have gone back, so we
                    # shift forward again and then force the zone to GMT
                    tValue = tValue.ShiftZone(
                        zDirection=1, zHour=1).WithZone(zDirection=0)
                    dataPoint['TimePoint'].SetFromValue(tValue)
                    logging.info(
                        "Auto-detecting switch to GMT at: %s", str(tValue))
                    try:
                        collection.InsertEntity(dataPoint)
                    except KeyError:
                        logging.error(
                            "Duplicate data point during BST/GMT switching: %s",
                            str(tValue))
                else:
                    logging.error(
                        "Unexpected duplicate data point: %s", str(tValue))


def LoadData(weatherData, dirName):
    for fileName in os.listdir(dirName):
        if not fileName[0:4].isdigit() or fileName[-1] == '~':
            # ignore odd files and some editor backups
            continue
        logging.info(
            "Loading data from file %s", os.path.join(dirName, fileName))
        year, month, day = map(int, fileName.split('_'))
        with open(os.path.join(dirName, fileName), 'r') as f:
            LoadDataFromFile(weatherData, f, year, month, day)


def LoadNotes(weatherNotes, fileName, weatherData):
    with open(fileName, 'r') as f:
        id = 1
        with weatherNotes.OpenCollection() as collection, weatherData.OpenCollection() as data:
            while True:
                line = f.readline()
                if len(line) == 0:
                    break
                elif line[0] == '#':
                    continue
                noteWords = line.split()
                if noteWords:
                    note = collection.NewEntity()
                    note['ID'].SetFromValue(id)
                    start = iso.TimePoint(
                        date=iso.Date.FromString(noteWords[0]),
                        time=iso.Time(hour=0, minute=0, second=0))
                    note['StartDate'].SetFromValue(start)
                    end = iso.TimePoint(
                        date=iso.Date.FromString(noteWords[1]).Offset(days=1),
                        time=iso.Time(hour=0, minute=0, second=0))
                    note['EndDate'].SetFromValue(end)
                    note['Details'].SetFromValue(
                        string.join(noteWords[2:], ' '))
                    collection.InsertEntity(note)
                    # now find the data points that match
                    data.Filter(
                        core.CommonExpression.FromString(
                            "TimePoint ge datetime'%s' and TimePoint lt datetime'%s'" %
                            (unicode(start), unicode(end))))
                    for dataPoint in data.values():
                        # use values, not itervalues to avoid this bug in Python 2.7
                        # http://bugs.python.org/issue10513
                        dataPoint['Note'].BindEntity(note)
                        data.UpdateEntity(dataPoint)
                    id = id + 1
    with weatherNotes.OpenCollection() as collection:
        collection.OrderBy(
            core.CommonExpression.OrderByFromString('StartDate desc'))
        for e in collection.itervalues():
            with e['DataPoints'].OpenCollection() as affectedData:
                print "%s-%s: %s (%i data points affected)" % (
                    unicode(e['StartDate'].value), unicode(e['EndDate'].value),
                    e['Details'].value, len(affectedData))


def DryRun():
    doc = LoadMetadata()
    container = InMemoryEntityContainer(
        doc.root.DataServices['WeatherSchema.CambridgeWeather'])
    weatherData = doc.root.DataServices[
        'WeatherSchema.CambridgeWeather.DataPoints']
    weatherNotes = doc.root.DataServices[
        'WeatherSchema.CambridgeWeather.Notes']
    LoadData(weatherData, SAMPLE_DIR)
    LoadNotes(weatherNotes, 'weathernotes.txt', weatherData)
    return doc.root.DataServices['WeatherSchema.CambridgeWeather']


def TestModel(drop=False):
    """Read and write some key value pairs"""
    doc = LoadMetadata()
    container = MakeContainer(doc, drop)
    weatherData = doc.root.DataServices[
        'WeatherSchema.CambridgeWeather.DataPoints']
    weatherNotes = doc.root.DataServices[
        'WeatherSchema.CambridgeWeather.Notes']
    if drop:
        LoadData(weatherData, SAMPLE_DIR)
        LoadNotes(weatherNotes, 'weathernotes.txt', weatherData)
    with weatherData.OpenCollection() as collection:
        collection.OrderBy(
            core.CommonExpression.OrderByFromString('WindSpeedMax desc'))
        collection.SetPage(30)
        for e in collection.iterpage():
            note = e['Note'].GetEntity()
            if e['WindSpeedMax'] and e['Pressure']:
                print "%s: Pressure %imb, max wind speed %0.1f knots (%0.1f mph); %s" % (unicode(e['TimePoint'].value),
                                                                                         e['Pressure'].value, e['WindSpeedMax'].value, e[
                                                                                             'WindSpeedMax'].value * 1.15078,
                                                                                         note['Details'] if note is not None else "")


def runWeatherServer(weatherApp=None):
    """Starts the web server running"""
    server = make_server('', SERVICE_PORT, weatherApp)
    logging.info("HTTP server on port %i running" % SERVICE_PORT)
    # Respond to requests until process is killed
    server.serve_forever()


def runWeatherLoader(container=None):
    """Starts a thread that monitors the DTG website for new values"""
    if container is None:
        doc = LoadMetadata()
        container = MakeContainer(doc)
    client = http.HTTPRequestManager()
    weatherData = container['DataPoints']
    DTG = "http://www.cl.cam.ac.uk/research/dtg/weather/daily-text.cgi?%s"
    with weatherData.OpenCollection() as collection:
        collection.OrderBy(
            core.CommonExpression.OrderByFromString('TimePoint desc'))
        sleepInterval = 60
        collection.SetPage(1)
        lastPoint = list(collection.iterpage())
        if lastPoint:
            lastPoint = lastPoint[0]['TimePoint'].value
        else:
            lastPoint = iso.TimePoint.FromString("19950630T000000Z")
        nextDay = lastPoint.date
        while True:
            today = iso.TimePoint.FromNowUTC().date
            if nextDay < today:
                # Load in nextDay
                logging.info("Requesting data for %s", str(nextDay))
                century, year, month, day = nextDay.GetCalendarDay()
                request = http.HTTPRequest(DTG % str(nextDay))
                client.ProcessRequest(request)
                if request.status == 200:
                    # process this file and move on to the next day
                    f = StringIO.StringIO(request.resBody)
                    LoadDataFromFile(
                        weatherData, f, century * 100 + year, month, day)
                    nextDay = nextDay.Offset(days=1)
                    if sleepInterval > 10:
                        sleepInterval = sleepInterval // 2
                else:
                    # back off and try again
                    sleepInterval = sleepInterval * 2
            else:
                # back off and try again
                sleepInterval = sleepInterval * 2
            client.IdleCleanup(0)
            if sleepInterval > 86400:
                sleepInterval = 86400
            time.sleep(sleepInterval)


def main():
    """Executed when we are launched"""
    doc = LoadMetadata()
    container = MakeContainer(doc)
    server = ReadOnlyServer(serviceRoot=SERVICE_ROOT)
    server.SetModel(doc)
    t = threading.Thread(
        target=runWeatherServer, kwargs={'weatherApp': server})
    t.setDaemon(True)
    t.start()
    logging.info("Starting HTTP server on %s" % SERVICE_ROOT)
    t.join()


if __name__ == '__main__':
    logging.basicConfig(level=logging.INFO)
    main()
